Distribution characteristics and formation mechanisms of progressive and standing waves in the Haitan Island coastal waters, Fujian

Haitan Island, situated at the northern entrance of the Taiwan Strait, is characterized by unique and complex flow field features exhibiting both standing and progressive wave properties. Through harmonic analysis of in-situ tidal current measurements and numerical simulation of the tidal flow field around Haitan Island, this study investigates the distribution characteristics of tidal currents and tides in the region. Results reveal that the timing of maximum current velocities in the M₂ tidal constituent ellipses (occurring between 3.5−5.0 hours) demonstrates distinct progressive wave characteristics, while phase lags of 1.0−2.0 hours indicate standing wave dominance. Pronounced progressive wave features are observed in the central Haitan Strait, the Changjiang Ao area northeast of Haitan Island, and the eastern offshore waters. The progressive waves in Changjiang Ao and eastern offshore areas maintain their characteristics due to minimal interference from land-reflected Pacific tidal waves, whereas tidal waves entering through the northern and southern openings of Haitan Strait partially form standing waves through coastal reflection superposition, while the remainder propagate as progressive waves in the central strait region.